It still can happen mainly from compatability issues with each other, and the more mods you have the higher chance. Some authors list if there's a problem, and others don't know. Just disable them a couple at a time or all from the same author and see when it fixes itself.

I have plenty more than 30 mods active, and this hasn't happened. I don't know what could be causing somethign like that, I'd recomment turning mods off and on in sets of five, see if that changes anything. If all else fails try verifying the integrity of your game cache.

I have had this game for a while on my laptop and i have had close to 30 mods and that didnt matter. This is on my desktop that i downloaded it on.I have deleted all my add ons and it still didnt work so...

It looks like you may have been affected from the last L4D2 update. In the last update, they deleted certain custom textures that were released with the Cold Stream map that they felt were not nessesary any more. Long story short....try this dude: Missing custom textures pack: http://www.l4dmaps.com/details.php?file=26132If this fails though......I`m really not sure how I can help you....

It looks like you may have been affected from the last L4D2 update. In the last update, they deleted certain custom textures that were released with the Cold Stream map that they felt were not nessesary any more. Long story short....try this dude: Missing custom textures pack: http://www.l4dmaps.com/details.php?file=26132If this fails though......I`m really not sure how I can help you....

That's missing stuff for custom campaigns and Cold Stream, mostly. While it is a great resource, I'm not sure it will help with official campaigns.